Cable and medical hollow tube

ABSTRACT

A cable includes a sheath, and a coating film covering a circumference of the sheath, the coating film adhering to the sheath. The coating film is formed from a rubber composition including a rubber component and fine particles. A static friction coefficient on a surface of the coating film is 0.5 or less. When the coating film is subjected to a testing such that a long fiber non-woven fabric including cotton linters including an alcohol for disinfection with a length of 50 mm along a wiping direction is brought contiguous to the surface of the coating film at a shearing stress of 2×10−3 MPa to 4×10−3 MPa, followed by wiping off the surface of the coating film at a speed of 80 times/min to 120 times/min and 20,000 repetitions thereof for a wiping direction length of 150 mm, a difference (an absolute value of a difference) between the static friction coefficients of the coating film before and after the testing is not greater than 0.1.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on Japanese patent application No.2019-167722 filed on Sep. 13, 2019 and Japanese patent application No.2020-031580 filed on Feb. 27, 2020, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a cable and a medical hollow tube.

2. Description of the Related Art

JP-A-2008-287 (Patent Document 1) and JP-A-2018-23758 (Patent Document2) discloses a technique on a medical coating composition, which canimpart a stable sliding property to a surface without applying alubricant to that surface.

-   [Patent Document 1] JP-A-2008-287-   [Patent Document 2] JP-A-2018-23758

SUMMARY OF THE INVENTION

A sheath made of an electrical insulating member is formed on a surfaceof a cable. This sheath is desired to have no stickiness or the like,but a good slidability (sliding property). On the other hand, an endportion of the cable is subjected to a termination, during which aprotective member such as a boot or the like is attached to the sheathwith an adhesive. Here, in the cable with the protective member havingbeen attached thereto, for example, when the end portion of the cable isbent, a coating film, which has been formed on a surface of the sheath,may be peeled off, which may lead to the protective member detachingfrom the cable. That is, the cable is required to have no stickiness orthe like but a good slidability on the surface of that cable, and aresistance of the coating film formed on the surface of the sheath tobeing peeled off.

Also, a medical hollow tube is provided with a coating film on an outersurface or an inner surface of a hollow tube main body. As with thecoating film of the cable, this coating film of the medical hollow tubeis required to have a good slidability, and a resistance of the coatingfilm formed on the outer surface or the inner surface of the hollow tubemain body to being peeled off.

From the aspect of good hygiene, on the other hand, it is necessary tokeep the surfaces of the cable or the medical hollow tube clean bywiping off them with a disinfecting alcohol. For that reason, thecoating film is required to have such a high resistance to being wipedoff as to maintain a high slidability, even when repeatedly wiped offwith the disinfecting alcohol or the like.

Accordingly, it is an object of the present invention to provide atechnique for allowing a coating film to develop a slidability and aresistance to being wiped off at a high level.

According to one aspect of the present invention, there is provided acable, comprising: a sheath; and a coating film covering a circumferenceof the sheath, the coating film adhering to the sheath, wherein thecoating film comprises a rubber composition including a rubber componentand fine particles, with a static friction coefficient on a surface ofthe coating film being 0.5 or less, wherein the coating film comprises aresistance to being wiped off in such a manner that, when the coatingfilm is subjected to a testing such that a long fiber non-woven fabricincluding cotton linters including a disinfecting alcohol with a lengthof 50 mm along a wiping direction is brought contiguous to the surfaceof the coating film at a shearing stress of 2×10⁻³ MPa to 4×10⁻³ MPa,followed by wiping off the surface of the coating film at a speed of 80times/min to 120 times/min and 20,000 repetitions thereof for a wipingdirection length of 150 mm, a difference (an absolute value of adifference) between the static friction coefficients of the coating filmbefore and after the testing is not greater than 0.1.

According to another aspect of the present invention, there is provideda medical hollow tube, comprising: a hollow tube main body including aninner surface and an outer surface; and a coating film covering at leastone of the inner surface and the outer surface of the hollow tube mainbody, the coating film adhering to the hollow tube main body, whereinthe coating film comprises a rubber composition including a rubbercomponent and fine particles, with a static friction coefficient on asurface of the coating film being 0.5 or less, wherein the coating filmcomprises a resistance to being wiped off in such a manner that, whenthe coating film is subjected to a testing such that a long fibernon-woven fabric including cotton linters including an alcohol fordisinfection with a length of 50 mm along a wiping direction is broughtcontiguous to the surface of the coating film at a shearing stress of2×10⁻³ MPa to 4×10⁻³ MPa, followed by wiping off the surface of thecoating film at a speed of 80 times/min to 120 times/min and 20,000repetitions thereof for a wiping direction length of 150 mm, adifference (an absolute value of a difference) between the staticfriction coefficients of the coating film before and after the testingis not greater than 0.1.

Points of the Invention

According to the present invention, it is possible to allow the coatingfilm to develop a slidability and a resistance to being wiped off at ahigh level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view perpendicular to a length direction ofa cable according to one embodiment of the present invention.

FIG. 2A is a diagram schematically showing a probe cable configured tobe connectable to an ultrasonic imaging device.

FIG. 2B is a cross-sectional view showing the probe cable taken alongline A-A of FIG. 2A.

FIG. 3A is a cross-sectional view schematically showing a surface of acoating film in the cable of one embodiment of the present invention;

FIG. 3B is a cross-sectional view schematically showing a surface of acoating film in a cable of a comparative example to the presentinvention;

FIG. 4A is a cross-sectional view showing a medical hollow tube providedwith an outer coating film on an outer surface of a hollow tube mainbody;

FIG. 4B is a cross-sectional view showing a medical hollow tube providedwith an inner coating film on an inner surface of a hollow tube mainbody;

FIG. 4C is a cross-sectional view showing a medical hollow tube providedwith an outer coating film and an inner coating film on an outer surfaceand an inner surface, respectively, of a hollow tube main body;

FIG. 5 is a diagram for explaining a method of producing an evaluationsample used for evaluating the adhesion strength between an underlyingsheath and an overlying coating film;

FIG. 6 is a diagram schematically showing a measuring method formeasuring the tensile shear strength using the evaluation sample;

FIG. 7 is a diagram schematically showing a bending resistance testingfor the probe cable;

FIG. 8A is a diagram for explaining a wiping off testing method;

FIG. 8B is a diagram for explaining a wiping direction length of acotton cloth and a wiping off length by moving the cotton cloth;

FIG. 9 is a diagram showing a change in the static friction coefficientof the coating film according to the number of times of wiping off;

FIG. 10A is an SEM image showing a coating film surface of a cable ofExample 1;

FIG. 10B is an SEM image showing a cross section of the coating film ofthe cable of Example 1;

FIG. 11A is an SEM image showing a coating film surface of a cable ofComparative Example 1;

FIG. 11B is an SEM image showing a cross section of the coating film ofthe cable of Comparative Example 1;

FIG. 12 is an SEM image showing a cross section of the coating film ofthe cable of Example 3;

FIG. 13 is an SEM image showing a coating film surface of a cable ofComparative Example 2;

FIG. 14 is a diagram showing a surface profile of the coating film ofExample 1; and

FIG. 15 is a diagram showing a surface profile of the coating film ofComparative Example 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Findings Obtained bythe Present Inventors

First, the findings obtained by the present inventors will be described.

For example, in an ultrasonic imaging device that is designed as amedical device, an ultrasonic probe is connected to a cable, so that amedical test is performed by moving that ultrasonic probe on a humanbody. At this point of time, if the cable connected to the ultrasonicprobe is sticky, the cable may be stuck by being brought into contactwith another cable or by being caused to touch a medical tester'sgarment or the like. As a result, the ultrasonic probe may be difficultto move smoothly, which may lead to impairing the handleability of themedical device.

Conventionally, from the point of view of ensuring the slidability ofthe cable, a polyvinyl chloride (PVC) has been used as a material forforming a sheath for the cable. It should be noted, however, that, withthe PVC, as the period of use of the cable becomes longer, an alterationof the sheath, such as a discoloring of the sheath, is more likely tooccur.

From this, in place of the PVC, a silicone rubber being excellent inheat resistance and chemical resistance has been studied as the sheathmaterial. It should be noted, however, that, since the sheath formed ofthe silicone rubber tends to be sticky (also termed tacky), the sheathformed of the silicone rubber tends to be low in slidability (slidingproperty).

In view of the foregoing, for the purpose of improving the slidabilityof the cable, providing a coating film having a small static frictioncoefficient on a surface of the sheath formed of the silicone rubber hasbeen proposed. As the coating film having a small static frictioncoefficient, the coating film formed of a rubber composition includingfine particles and having micro irregularities produced by the fineparticles on its surface has been studied.

However, according to the present inventors' study, it has been foundout that the cable provided with the above-described coating film,though having the resulting slidability, has the following two problems.

One of the two problems is that not enough adhesion strength between thecoating film and the sheath can be ensured. When the cable is used as,e.g., a probe cable, a boot may be attached to a terminal of the cableas a protective member. At this point of time, the boot is attached tothe coating film formed on the outermost surface of the cable with anadhesive between the boot and the coating film. However, the adhesionstrength between the underlying sheath and the overlying coating film islow, and therefore, when the boot attached to the cable is acted on by abending pressure, a peeling off of the coating film may occur at theinterface between it and the underlying sheath, which may lead to theboot detaching from the cable.

The other one of the two problems is that the coating film is low inresistance to being wiped off. The cable for medical use is usedrepeatedly by being wiped off with a disinfecting alcohol or the like tokeep its surface clean. According to the present inventors' study,however, it has been found that the irregular state of the coating filmsurface is changed by the repeating of the wiping off of the coatingfilm surface, which increases the static friction coefficient of thecoating film with the increase of the number of times the coating filmis wiped off, and which makes it difficult to obtain the desiredslidability of the cable. In other words, the coating film may be unableto maintain the slidability of the cable at a high level over a longperiod of use.

As a result of the study on the above two problems, the presentinventors have found out that a factor that degrades the variousproperties of the coating film is air bubbles present in the coatingfilm. The air bubbles are the ones formed when a liquid material to beused to form the coating film is cured. The presence of these airbubbles in the surface of the coating film to be brought contiguous tothe sheath leads to a lessening in the area of the adhesion of thecoating film to the sheath, and therefore a lowering in the strength ofthe adhesion of the coating film to the sheath. Further, on the otherhand, the presence of the air bubbles in the surface of the coating filmmay lead to formation of a collapse (a collapsed portion), and an edgeof such a collapsed portion on the surface of the coating film may leadto the occurrence of being stuck at that edge when the surface of thecoating film is wiped off. For that reason, the coating film tends to bescraped off during being wiped off, and its slidability is likely to belowered by the repeating of the wiping off of the coating film surface.Furthermore, the air bubbles disrupt the dense distribution of the fineparticles on the surface of the coating film, and greatly affect theirregular state of the coating film surface, and therefore the variousproperties of the coating film produced by the irregularities on thesurface of the coating film.

From these points, as a result of the study to reduce the air bubbles(voids) present in the coating film by suppressing the formation of theair bubbles when the coating film is cured and formed, the presentinventors have found out that it is possible to allow the coating filmto achieve its slidability, adhesion strength and resistance to beingwiped off at a high level and in a well-balanced manner.

The present invention has been made based on the above findings.

One Embodiment of the Present Invention

Hereinafter, one embodiment of the present invention will be describedby taking a medical device cable, which is configured to be connectableto a medical device, as one example, and by using the drawings. Notethat, in all the drawings for describing the embodiment, the samemembers are denoted by the same reference characters in principle, andthe repeated descriptions thereof will be omitted. Further, hatching maybe used even in a plan view to make the drawings easy to understand.

[Cable]

As shown in FIG. 1 , a medical device cable 10 of the present embodiment(hereinafter, also referred to as simply the cable 10) is configured insuch a manner that a sheath 13 and a coating film 14 are in turn stackedover an outer periphery of a cable core 11.

(Cable Core)

The cable core 11 is constituted by laying a plurality of electric wires11 a together and coating an outer periphery of the plurality ofelectric wires 11 a laid together with a shield 12. Examples of theelectric wire 11 a to be able to be used include: an electric wirecomposed of a conductor made of a solid wire or a stranded wire such asa pure copper wire or a tin-plated copper wire or the like, and anelectrical insulating member covering an outer periphery of thatconductor, a coaxial cable, an optical fiber, and the like. As theshield 12, for example, a braided wire or the like can be used.

(Sheath)

The sheath 13 is formed of an electrical insulating material, and iscovering the cable core 11. The electrical insulating material is notparticularly limited as long as it is capable to be used in the sheath13, but examples of the electrical insulating material to be able to beused include: a silicone rubber, a polyethylene, a chlorinatedpolyethylene, a chloroprene rubber, a polyvinyl chloride (PVC), and thelike. Among them, the silicone rubber or the chloroprene rubber ispreferable from the point of view of the chemical resistance and theheat resistance. Note that the electrical insulating material to formthe sheath may be added with general compounding agents such as eachtype of crosslinking agents, crosslinking catalysts, antioxidants,plasticizers, lubricants, fillers, flame retardants, stabilizers,coloring agents and the like.

(Coating Film)

The coating film 14 is covering the sheath 13. The coating film 14 isformed from a rubber composition including fine particles and a rubbercomponent, and is configured in such a manner that the fine particlesare finely dispersed in the rubber component. A surface of the coatingfilm 14 is formed with irregularities derived from the fine particles.The above irregularities on the surface of the coating film 14 are ableto make small the contact area of the coating film 14 when the coatingfilm 14 is brought into contact with another member, and are thereforeable to make the static friction coefficient of the coating film 14smaller than the static friction coefficient inherent in the rubbercomponent constituting the coating film 14. This coating film 14 iscapable to make the slidability of the cable 10 high as compared withthe case where the sheath 13 is present at the surface of the cable 10.

The static friction coefficient of the coating film 14 is notparticularly limited, but is preferably 0.5 or less from the point ofview of imparting the desired slidability to the cable 10.

Also, since the fine particles are densely distributed on the surface ofthe coating film 14, the coating film 14 is high in the resistance tobeing wiped off. Specifically, when the coating film 14 is subjected toa testing such that a long fiber non-woven fabric including cottonlinters including a disinfecting alcohol (hereinafter, also referred toas “cotton cloth”) with a length of 50 mm along a wiping direction isbrought contiguous to the surface of the coating film at a shearingstress of 2×10⁻³ MPa to 4×10⁻³ MPa, followed by wiping off the surfaceof the coating film 14 at a speed of 80 times/min to 120 times/min (40cycles/min to 60 cycles/min) and 20,000 repetitions (10,000 cycles)thereof for a wiping direction length of 150 mm, a difference (anabsolute value of a difference) between the static friction coefficientsof the coating film before and after the testing can be reduced to notgreater than 0.1, preferably not greater than 0.05. That is, even whenthe coating film 14 is repeatedly wiped off, its surface irregularitiescan be maintained, and the slidability produced by the surfaceirregularities of the coating film 14 can be maintained over a longperiod of time. Here, a “cotton cloth length” is a length of the cottoncloth along the wiping direction, and a “wiping direction length” is alength of a part of the cable sheath on which complete wiping isperformed by moving the cotton cloth when the surface of the coatingfilm 14 is wiped off with the cotton cloth. The “shearing stress” is apulling force (a resistance in pulling out) generated when pulling outthe cable from the cotton cloth while pressing the cable by the cottoncloth impregnated with the disinfecting alcohol.

An amount of the disinfecting alcohol to impregnate the cotton clothshould be equal to or more than an amount enough for spreading entirelyover the cotton cloth. For example, in general, the amount of thedisinfecting alcohol to impregnate a surgical gauze is 5 ml to 6 ml per1 g of the cotton cloth. Since the weight (size) of the cotton clothdepends on an outer diameter of the cable to be wiped off, the weight ofthe cotton cloth to be used is previously measured and the impregnationamount is adjusted in accordance with the measured weight. For example,when a cable with an outer diameter of 6.7 mm is used, a cotton cloth(“BEMCOT regular type (M-3II)” available from Asahi Kasei Corporation)with a weight of approximately 0.25 g to 0.30 g is required, it ispreferable that the cotton cloth is impregnated with an amount of 2.0 mlof the disinfecting alcohol which sufficiently satisfies the abovestandard.

In addition, in the present embodiment, as will be described in detaillater, since the formation of the air bubbles during the curing of therubber composition is suppressed, the air bubbles (voids) present in thecoating film 14 can be reduced. For that reason, it is possible tosuppress a decrease in the contact area of the sheath 13 side surface ofthe coating film 14 due to the air bubbles (voids). This allows thecontact area between the overlying coating film 14 and the underlyingsheath 13 to be held large, and the adhesion strength between theoverlying coating film 14 and the underlying sheath 13 to be made higherthan when the air bubbles are present in the coating film 14.Specifically, the adhesion strength between the overlying coating film14 and the underlying sheath 13 can be set at not lower than 0.3 MPa.Note that the upper limit of the adhesion strength between theunderlying sheath 13 and the overlying coating film 14 is notparticularly limited, but, in practice, is on the order of 0.7 MPa.

Further, since the air bubbles can be reduced also in the frontside(upper) surface of the coating film 14, the occurrence of a collapseformation due to the air bubbles can be reduced in the frontside (upper)surface of the coating film 14. Since no fine particles can be presentat the collapse formation part of the coating film 14, the occurrence ofa collapse formation leads to a lessening in the region of the coatingfilm 14 where the fine particles can be distributed. This leads to alessening in the number of the fine particles distributed on the surfaceof the coating film 14. That is, the distribution of the fine particlesbecomes sparse. In addition, since a plurality of the fine particleseasily aggregate to form coarse aggregated particles, it is difficult toproduce the desired surface irregularities. On the other hand, byreducing the occurrence of a collapse formation, it is possible toincrease the number of the fine particles occupying the surface of thecoating film 14, or suppress the occurrence of an aggregation of thefine particles, and it is therefore possible to more densely distributethe fine particles on the surface of the coating film 14.

Also, since the fine particles are densely distributed on the surface ofthe coating film 14, there is little variation in the number of the fineparticles by region. Specifically, it is preferable that, when thenumber of the fine particles per unit area is measured in any pluralityof parts of the surface of the coating film 14, a number distribution,which is calculated from a formula (N_(max)−N_(min))/+N_(min))×100 whereN_(max) is a maximum value of the number of the fine particles per unitarea and N_(min) is a minimum value of the number of the fine particlesper unit area, is 5% or less. The smaller the number distribution, thesmaller the deviation in the number of the fine particles, whichindicates that the variation in the distribution of the fine particlesis lessened.

In addition, it is preferable that the number of voids, which are formedby the air bubbles, is lessened in the surface of the coating film 14,and it is preferable that substantially no void is present in thesurface of the coating film 14. Specifically, when observed with anelectron microscope SEM in a condition of a magnification of 1000 times,the number of voids having a size of not smaller than 1 μm present perunit area is preferably not more than 5/40 μm square, and morepreferably, substantially no void having a size of 10 μm or more ispresent in the surface of the coating film 14.

On the surface of the coating film 14, the number of collapsed portionspresent, which are formed by the voids, may be lessened, while thenumber of projecting portions present, which are formed by the fineparticles, may be increased. That is, it is preferable that the surfaceof the coating film 14 has the surface irregularities formed principallyfrom the projecting portions.

The thickness of the coating film 14 is not particularly limited, but ispreferably not thinner than 3 μm and not thicker than 100 μm. When thethickness of the coating film 14 is set at not thinner than 3 μm, thepredetermined resistance to being wiped off can be imparted to thecoating film 14. Further, when the thickness of the coating film 14 isset at not thicker than 100 μm, the flexibility or bendability of thecable 10 can be held high.

(Rubber Composition for Coating Film Formation)

Next, the rubber composition for forming the coating film 14 will bedescribed.

The rubber composition is a cured product, which is produced by curing aliquid rubber composition (hereinafter, also referred to as the coatingmaterial) including a liquid rubber, fine particles, a curing catalyst,and, if desired, other additives, and the rubber component is configuredto include the cured rubber component and the fine particles.

The rubber component is a matrix component constituting the coating film14. A silicone rubber can be used as the rubber component. There are twotypes of silicone rubbers: a condensation reaction type silicone rubberand an addition reaction type silicone rubber, depending on curingmethods, but among them, the addition reaction type silicone rubber ispreferable. The addition reaction type silicone rubber is resistant toproducing the air bubbles during curing as compared with thecondensation reaction type silicone rubber, and is therefore able tomake the distribution of the fine particles in the coating film 14denser.

The addition reaction type silicone rubber is produced by curing aliquid silicone rubber composition by an addition reaction. The liquidsilicone rubber composition contains, for example, an organopolysiloxanehaving a vinyl group (CH₂═CH—) and an organohydrogen polysiloxane havinga hydrosilyl group (Si—H). The organopolysiloxane serves as a basepolymer for the silicone rubber. The organohydrogen polysiloxane servesas a crosslinking agent for the base polymer. For example, by mixing aplatinum catalyst, the organohydrogen polysiloxane undergoes ahydrosilylation reaction between the hydrosilyl group and the vinylgroup in the base polymer, thereby crosslinking and curing the basepolymer. The organopolysiloxane and the organohydrogen polysiloxane arenot particularly limited, but the convintionally knownorganopolysiloxane and organohydrogen polysiloxane can be used.

Also, a chloroprene rubber may be used as the rubber component, and thecoating film 14 may be configured to include the chloroprene rubber.

The fine particles are dispersed in the rubber component to form theprojecting portions, which are formed on the surface of the coating film14. As the fine particles, it is preferable to use at least any fineparticles of silicone rubber fine particles, silicone resin fineparticles and silica fine particles. The types of the fine particles canbe appropriately altered according to the required properties of thecoating film 14.

Specifically, it is preferable that the fine particles have a higherhardness than that of the coating film 14 from the point of view ofmaintaining the surface irregularities shape of the coating film 14 andensuring the slidability of the coating film 14 when an object isbrought into contact with the coating film 14. Specifically, it ispreferable that the fine particles have a Shore (durometer A) hardnessof not lower than 1.1 times the hardness of the cured productconstituting the coating film 14. This is because the higher thehardness of the fine particles, the more resistant the fine particlesare to being deformed by the pressing pressure when an object is broughtinto contact with the surface of the coating film 14, and the moreeasily the surface irregularities shape of the coating film 14 ismaintained. Since the hardness becomes high in the order of the siliconerubber, the silicone resin, and the silica, the silica fine particlesare preferred from the point of view of the hardness.

On the other hand, from the point of view of uniformly distributing thefine particles on the surface of the coating film 14 and forming thedesired surface irregularities of the coating film 14, the fineparticles are preferably small in mass. This is because if the fineparticles are large in mass, the fine particles settle before thecoating material is cured to form the coating film 14, so the fineparticles become resistant to forming the moderate irregularities on thesurface of the coating film 14. In this regard, by making the fineparticles small in mass, the settling of the fine particles issuppressed, and the moderate irregularities are easily formed on thesurface of the coating film 14. Since the mass becomes large in theorder of the silicone rubber, the silicone resin, and the silica, thesilicone rubber particles are preferable from the point of view of themass.

Namely, the silicone resin fine particles are preferable from the pointof view of both maintaining the surface irregularities shape of thecoating film 14 to ensure the slidability of the surface of the coatingfilm 14, and uniformly distributing the fine particles on the surface ofthe coating film 14 to easily form the desired surface irregularities ofthe coating film 14.

The quantity of the fine particles to be contained in the rubbercomposition is preferably not lower than 10% by mass and not higher than60% by mass. By setting the quantity of the fine particles to becontained in the rubber composition at not lower than 10% by mass, it ispossible to form the irregularities on the surface of the coating film14, so it is possible to make the static friction coefficient of thecoating film 14 small and thereby impart the desired slidability to thesurface of the coating film 14. On the other hand, if the quantity ofthe fine particles to be contained in the rubber composition isexcessively large, the strength of the coating film 14 may be lowered,but, by setting the quantity of the fine particles to be contained inthe rubber composition at not higher than 60% by mass, it is possible tomaintain the strength of the coating film 14 while obtaining theslidability of the surface of the coating film 14. Note that thequantity of the fine particles to be contained in the rubber compositionis calculated on the assumption that the coating material is cured withsubstantially no decrease in mass, and refers to the proportion of thefine particles to the cured coating film 14 (the total of the rubbercomponent and the fine particles). In other words, the content of thefine particles is preferably 10% by mass to 60% by mass of the total ofthe rubber component and fine particles.

The sizes of the fine particles may be appropriately altered accordingto the thickness of the coating film 14, and are not particularlylimited. From the point of view of forming the desired irregularities onthe surface of the coating film 14, the average particle diameter of thefine particles is preferably 1 μm or more and 10 μm or less. Here, theaverage particle diameter refers to the one measured by a laserdiffraction scattering method. By setting the average particle diameterof the fine particles at not smaller than 1 μm, it is easy to form themoderate irregularities on the surface of the coating film 14, so it ispossible to make the static friction coefficient of the coating film 14small and thereby make the slidability of the coating film 14 higher.Moreover, since the masses of the fine particles can be adjusted to anappropriate magnitude by setting the average particle diameter of thefine particles at not larger than 10 μm, it is possible to suppress theoccurrence of a settling of the fine particles and the occurrence of anuneven coating during coating with the liquid rubber composition.

The curing catalyst is not particularly limited as long as it is capableto promote the addition reaction, but, for example, a platinum or aplatinum-based compound may be used as the curing catalyst.

The other additives may be compounded if desired. For example, anorganic solvent can be used for the purpose of adjusting the viscosityof the coating material. Examples of the organic solvent to be able tobe used include: aromatic hydrocarbon-based solvents such as toluene,xylene and the like, and aliphatic hydrocarbon-based solvents such asn-hexane, n-heptane, n-octane, isooctane, nonane, decane, undecane,dodecane and the like. The above organic solvents can be used alone orin combination of two or more. Further, for example, alcohols such asethanol, isopropyl alcohol and the like, or acetone can be used as theorganic solvent.

The viscosity of the coating material is not particularly limited, butis preferably not lower than 1 mPa·s and not higher than 100 mPa·s fromthe point of view of densely distributing the fine particles. When theviscosity of the coating material is within the above range, it ispossible to appropriately alter the thickness of the coating film 14 aswell. Note that the viscosity of the coating material is measured at atemperature of 25±2 degrees C. using a tuning fork vibrating viscometer(SV-H, available from A & D Corporation).

Furthermore, for example, it is preferable to add a fumed silica havinga smaller particle diameter than those of the fine particles to therubber composition from the point of view of forming the desiredirregularities on the surface of the coating film 14. The fumed silicais produced by burning a raw material silicon chloride at a hightemperature, and refers to ultrafine silica particles having an averageprimary particle diameter of e.g. not smaller than 10 nm and not largerthan 30 nm. The fumed silica is classified into a hydrophilic fumedsilica having a silanol group (Si—OH) on its surface and a hydrophobicfumed silica produced by chemically reacting the silanol group on itssurface, but both the hydrophilic fumed silica and the hydrophobic fumedsilica can be used. The fumed silica is excellent in dispersibility inthe coating material and contributes to enhancing the dispersibility ofthe fine particles in the coating material. As a result, the settling ofthe fine particles in the coating material can be suppressed, andtherefore the desired irregularities can be formed on the surface of thecoating film 14.

The quantity of the fumed silica to be contained in the rubbercomposition is not particularly limited, but is preferably not lowerthan 0.1% by mass and 0.5 or less % by mass. Note that, herein, thequantity of the fumed silica to be contained in the rubber composition,is calculated in the same manner as the case of the fine particles, onthe assumption that the coating material is cured with substantially nodecrease in mass, and refers to the proportion of the fumed silica to100 parts by mass of the cured rubber component.

[Cable Producing Method]

Next, a method for producing the above-described cable 10 will bedescribed.

First, a plurality of (e.g., 100 or more) electric wires 11 a such ascoaxial cables or the like are bundled together. For example, a braidedshield is formed as the shield 12 to coat the bundle of the plurality ofelectric wires 11 a. This results in the cable core 11.

Next, the sheath material including, for example, the silicone rubber isextruded to coat the surface of the cable core 11 to form the sheath 13thereon.

From the viewpoint of increasing the adhesion between the coating film14 and the sheath 13, it is preferable to add an infrared absorber to amaterial of the sheath. By the addition of the infrared absorber, whenthe coating film 14 is heated by a heater, the sheath 13 absorbs moreinfrared rays and is more easily heated from the side of the sheath 13.Therefore, in the coating of the rubber composition, it is possible toreduce the uneven curing in the thickness direction and accelerate thecuring a deep part distant from the surface (i.e. a part closer to thesheath 13). As a result, the adhesion strength between the coating film14 thus obtained and the sheath 13 can be further increased. Inaddition, it is possible to shorten the time for curing the coating ofthe rubber composition by heating.

The infrared absorber is not specifically limited, and e.g. CoO, Fe₂O₃,MnO₂, Cr₂O₃, CuO, NiO, TiO₂ (oxidized titanium), C (carbon) and the likemay be used.

The content of the infrared absorber is not particularly limited, aslong as the performance of the sheath is not significantly deteriorated.From the viewpoint of increasing the adhesion between the coating film14 and the sheath 13, the content of the infrared absorber is preferably0.1% by mass or more. Meanwhile, if the content of the infrared absorberis excessively large, the sheath 13 will be fragile so that the tearstrength may be deteriorated. Therefore, from the viewpoint ofmaintaining high tear strength, the content of the infrared absorber ispreferably 10% by mass or less. Note that the content of the infraredabsorber is the proportion of the infrared absorber to 100 parts by massof the sheath material.

Next, the coating material is applied to the surface of the sheath 13 toform a coating material layer thereon. The method for applying thecoating material is not particularly limited, but may be appropriatelyselected from, for example, a dipping method, a spray coating method, aroll coating method and the like. Among these, the dipping method ispreferred.

The dipping method is designed as the method of forming the coatingmaterial layer on the surface of the sheath 13 by, e.g., immersing awire rod formed with the sheath 13 thereon in the coating material andpulling up that wire rod. Since the dipping method is capable to makethe thickness of the coating material layer uniform, the film thicknessof the coating film 14 can be formed uniformly in a length direction ofthe wire rod. In addition, by adjusting the pulling up speed for thecable 10, the distribution of the fine particles in the coating film 14can be more densely controlled. Hereinafter, this point will bedescribed.

In the dipping method, when the cable 10 is pulled up from the liquidlevel of the coating material, the coating material adheres to thesurface of the cable 10. When the coating material adheres to thesurface of the cable 10, the fine particles may be moving andself-ordering in the coating material layer. This self-ordering allowsthe fine particles to be densely distributed on the surface of thecoating material layer. And, the slower the cable pulling up speed, themore the time to be able to be ensured for the self-ordering of the fineparticles, and the more stably the densely distributed state of the fineparticles can be reproduced.

Specifically, from the point of view of densely dispersing the fineparticles, the pulling up speed for the cable 10 is preferably nothigher than 10 m/min, more preferably not higher than 5 m/min. On theother hand, from the point of view of the productivity of the coatingfilm 14, it is preferable to set the pulling up speed for the cable 10at not lower than 1 m/min. In other words, by setting the pulling upspeed for the cable 10 at not lower than 1 m/min and not higher than 5m/min, it is possible to make the distribution of the fine particles inthe surface of the coating film 14 denser while maintaining theproductivity of the coating film 14.

Next, the coating material layer is dried and cured by heating to formthe coating film 14 having the predetermined surface irregularities. Theheating temperature is not particularly limited, but may be set at, forexample, 120 degrees C. to 200 degrees C.

In heating of the coating, it is preferable to use an infrared heaterwhen the infrared absorber is added to the sheath 13. By heating thecoating with the use of the infrared heater, it is possible toaccelerate the heating of the sheath 13 and to suppress the unevencuring in the thickness direction of the coating film 14 to be obtained.As a result, the adhesion strength between the coating film 14 and thesheath 13 can be further increased. In addition, it is possible toshorten the time for curing the coating until the coating film 14,thereby improve the producibility of the cable 10.

This results in the cable 10 of the present embodiment.

[Probe Cable]

As shown in FIG. 2A, for example, a probe cable 20 is configured in sucha manner that an ultrasonic probe terminal 23 (hereinafter, alsoreferred to as simply a terminal 23) and a protective member 22 forprotecting that terminal 23 are attached to one end of the cable 10,while a connector 24 is attached to the other end of the cable 10. Theterminal 23 is connected to, for example, an ultrasonic probe, while theconnector 24 is connected to, for example, a main body portion of theultrasonic imaging device. The protective member 22 is a so-called boot,and as shown in FIG. 2B, is fitted over the coating film 14 to cover thecoating film 14 with an adhesion layer 21 therebetween. The adhesionlayer 21 is formed of, for example, a silicone based adhesive or anepoxy-based adhesive.

Advantageous Effects of the Present Embodiment

According to the present embodiment, one or more of the followingadvantageous effects are achieved.

(a) In the cable 10 of the present embodiment, the coating film 14 madeof the rubber composition including the rubber component and the fineparticles is provided on the surface of the sheath 13. At this point oftime, the addition reaction type silicone rubber is used as the rubbercomponent. The addition reaction type silicone rubber is capable tolessen the number of the air bubbles formed during the curing reaction,as compared with the condensation reaction type silicone rubber. Thismakes it possible to suppress the formation of voids, which are derivedfrom the air bubbles, in the surface of the coating film 14 beingcontiguous to the sheath 13. As a result, the area where the coatingfilm 14 is in contact with the sheath 13 can be maintained without beingreduced, and the high adhesion strength between the overlying coatingfilm 14 and the underlying sheath 13 can be ensured. In addition, it ispossible to allow the adhesion strength between the underlying sheath 13and the overlying coating film 14 to be not lower than 0.30 MPa, withoutforming the surface of the sheath 13 with a special layer for enhancingthe adhesion strength between the overlying coating film 14 and theunderlying sheath 13, (such as, for example, an adhesion strengthreinforcing layer made of a primer or a silane coupling agent or thelike, a layer having its surface modified by a method that performs aflame treatment that exposes the surface to flame for a short time, or amethod that performs a plasma treatment that ionizes or radicalizes agas and allows the ionized or radicalized gas to collide with thesurface, or a method that performs a corona treatment that ionizes aircomponents in atmospheric discharge and exposes the surface to theionized air components, or the like), before the formation of thecoating film 14. It should be noted, however, that the foregoing doesnot exclude the provision of the above special layer in order to furtherincrease the adhesion strength between the overlying coating film 14 andthe underlying sheath 13. Further, since the addition reaction typesilicone rubber also allows the number of voids in the coating film 14to be reduced, the advantageous effect of enhancing the strength of thecoating film 14 itself as well can be expected.

(b) In addition, since the formation of voids in the surface of thecoating film 14 can be suppressed, the number of the fine particlesoccupying the surface of the coating film 14 can be increased, or theoccurrence of an aggregation of the fine particles can be suppressed,and so the fine particles can be more densely distributed on the surfaceof the coating film 14. This makes it possible to form the desiredirregularities on the surface of the coating film 14, therefore makingthe static friction coefficient of the coating film 14 smaller than thatof the sheath 13 to be able to achieve the high slidability of thecoating film 14.

(c) Moreover, since the collapse formation on the surface of the coatingfilm 14 due to the void formation is lessened, when the surface of thecoating film 14 is repeatedly wiped off with a cotton cloth or the like,it is possible to prevent the cotton cloth from being stuck at the edgeof the collapse and damaging the coating film 14. This makes it possibleto keep the static friction coefficient on the surface of the coatingfilm 14 small even when the surface of the coating film 14 is repeatedlywiped off, and therefore makes it possible to achieve the highresistance of the surface of the coating film 14 to being wiped off.Specifically, when the coating film 14 is subjected to a testing suchthat the cotton cloth including a disinfecting alcohol (with a length of50 mm along a wiping direction) is brought contiguous to the surface ofthe coating film at a shearing stress of 2×10⁻³ MPa to 4×10⁻³ MPa,followed by wiping off the surface of the coating film 14 at a speed of80 times/min to 120 times/min (40 cycles/min to 60 cycles/min) and20,000 repetitions (10,000 cycles), a difference (an absolute value of adifference) between the static friction coefficients of the coating filmbefore and after the testing can be reduced to not greater than 0.1,preferably not greater than 0.05.

(d) Further, the coating film 14 is preferably formed by the dippingmethod using the coating material including the liquid rubber and thefine particles. The dipping method makes it possible to, when the cable10 is pulled out from the liquid surface of the coating material tothereby allow the coating material to adhere to the surface of the cable10, the self-ordering of the fine particles in the coating material canbe promoted, and the fine particles can therefore be more denselydistributed on the surface of the coating film 14.

(e) In addition, in the dipping method, it is preferable that thepulling up speed for the cable 10 be set at not lower than 1 m/min andnot higher than 10 m/min. By pulling up the cable 10 at the speed of notlower than 1 m/min and not higher than 10 m/min, the time taken for theself-ordering of the fine particles can be ensured, and the productivityof the coating film 14 can be kept high. This makes it possible to moredensely distribute the fine particles on the surface of the coating film14.

(f) The static friction coefficient on the surface of the coating film14 is 0.5 or less, preferably not higher than 0.3, and more preferablynot higher than 0.22. In the present embodiment, by forming theirregularities on the surface of the coating film 14, the staticfriction coefficient on the surface of the coating film 14 can be madesmaller than the static friction coefficient inherent in the rubbercomponent constituting the coating film 14, and can be reduced to 0.5 orless. By setting the static friction coefficient on the surface of thecoating film 14 at 0.5 or less, it is possible to achieve the highslidability such that the cable 10 is not stuck when being brought intocontact with another cable 10.

(g) Since the fine particles are densely distributed on the surface ofthe coating film 14, the numbers of the fine particles distributed ineach of a plurality of locations optionally selected on the surface ofthe coating film 14 are not greatly different from each other, and thevariations in the numbers of the fine particles distributed in each ofthe plurality of locations are lessened. Specifically, when the numberof the fine particles per unit area is measured in any plurality ofparts of the surface of the coating film 14, the number distribution,which is calculated from the formula(N_(max)−N_(min))/(N_(max)+N_(min))×100 where N_(max) is the maximumvalue of the number of the fine particles per unit area and N_(min) isthe minimum value of the number of the fine particles per unit area, ispreferably not more than 5%. By distributing the fine particles denselyand uniformly on the surface of the coating film 14 in this manner, theslidability of the coating film 14 and the resistance of the coatingfilm 14 to being wiped off can be made higher.

(h) In the surface of the coating film 14, the number of the voidshaving a size of not smaller than 1 μm per unit area is preferably notmore than 5/40 μm square, and more preferably, there is substantially novoid having such a size as to be able to be measured with the electronmicroscope. By lessening the number of the voids, the fine particles canbe more densely distributed on the surface of the coating film 14, andso the slidability of the coating film 14 and the resistance of thecoating film 14 to being wiped off can be made higher.

(i) In the coating film 14, since the collapsed portion due to thecollapse formation can be suppressed, the surface irregularities can beconfigured principally with the projecting portions formed by the fineparticles. This makes it possible to make the resistance of the coatingfilm 14 to being wiped off high. Hereinafter, this point will bespecifically described.

For example, as shown in FIG. 3B, when the coating film 14′ is formed ofthe condensation reaction type silicone rubber, voids 34 derived fromthe air bubbles are formed in the coating film 14′. When these voids 34are present in the surface, collapses 33 (collapsed portions 33) areformed. In that coating film 14′, when that coating film 14′ is wipedoff with a cotton cloth, the cotton cloth tends to be stuck at the edgesof the openings of the collapses 33. When the cotton cloth is stuck, thecoating film 14′ is scraped off, and the repetitions of the scraping offof the coating film 14′ cause the desorption of the fine particles 31from the coating film 14′, and the subsequent gradual removal of theprojecting portions 32 of the coating film 14′. As a result, the staticfriction coefficient of the coating film 14′ fails to be kept small, andthe slidability of the coating film 14′ is gradually impaired.

On the other hand, as shown in FIG. 3A, by suppressing the occurrence ofthe collapse formation due to the void formation in the surface of thecoating film 14, it is possible to increase the number of the projectingportions 32 formed by the fine particles 31. This coating film 14,though having the surface irregularities, is resistant to the occurrenceof the deep collapse formation, and is therefore able to suppress theoccurrence of the cotton cloth being stuck, and keep the static frictioncoefficient of the coating film 14 small even when the coating film 14is repeatedly wiped off. That is, the resistance of the coating film 14to being wiped off can be made higher.

(j) The fine particles 31 are preferably higher in hardness than therubber component forming the coating film 14. The above fine particles31 make it easy to maintain the surface irregularities shape of thecoating film 14, and therefore make it possible to achieve the desiredslidability of the coating film 14.

(k) As the fine particles 31, it is preferable to use at least any fineparticles of the silicone resin fine particles, the silicone rubber fineparticles and the silica fine particles. The silica fine particles arehigh in the hardness, and therefore make it easy to ensure theslidability of the coating film 14. Further, the silicone rubber fineparticles are relatively small in mass, and are therefore resistant tosettling during coating with the coating material, and able to form themoderate irregularities on the surface of the coating film 14. Thesilicone resin fine particles are intermediate in both the hardness andthe mass between the silicone rubber fine particles and the silica fineparticles, and therefore make it easy to form the desired surfaceirregularities shape, and also make it easy to maintain the surfaceirregularities shape and ensure the slidability of the coating film 14.

(l) Further, the rubber composition preferably further contains thefumed silica. The fumed silica is capable to suppress the occurrence ofthe settling of the fine particles in the coating material, andtherefore makes it possible to form the coating film 14 having itsslidability, adhesion strength and resistance to being wiped off at ahigh level and in a well-balanced manner.

(m) Still further, it is preferable that the sheath 13 further includesan infrared absorber. By the addition of the infrared absorber, when therubber composition is heated by the infrared heater, the sheath 13absorbs more infrared rays and the rubber composition is more easilyheated from the side of the sheath 13. Therefore, it is possible tosuppress the uneven curing in the thickness direction of the coatingfilm 14, thereby further improve the adhesion strength between thecoating film 14 and the sheath 13.

(n) In the probe cable 20, the protective member 22 is fitted over thecoating film 14 at one end of the cable 10 with the adhesion layer 21between it and the coating film 14. In the present embodiment, since theadhesion strength between the overlying coating film 14 and theunderlying sheath 13 can be made high, for example even when theprotective member 22 is acted on by a bending pressure, it is possibleto suppress the occurrence of a peeling of the coating film 14 from thesheath 13 and a subsequent detaching of the protective member 22. Inaddition, since the coating film 14 having the irregularities on itssurface is excellent in the slidability, for example when the ultrasonicprobe connected to the probe cable 20 is moved, and even if the probecable 20 is brought into contact with another probe cable 20, it ispossible to suppress the occurrence of being stuck. Further, since thecoating film 14 is excellent in the resistance to being wiped off, evenwhen the coating film 14 is repeatedly wiped off with a cotton cloth, itis possible to suppress the occurrence of damage or abrasion to thecoating film 14, and maintain the slidability of the coating film 14over a long period of time. Further, since the coating film 14 formed ofthe silicone rubber is excellent in chemical resistance and heatresistance, even when the coating film 14 is cleaned with a chemicalsuch as a disinfecting alcohol or the like or heated, the alteration inthe properties of the coating film 14 can be suppressed.

Other Embodiments

In the above embodiment, the case where the coating film 14 is providedon the probe cable 20 has been described, but the present invention isnot limited to this. For example, a medical cable other than the probecable 20 (such as an endoscope cable or a connection cable for acatheter) or a cabtire cable or the like can also be provided with theabove-described coating film.

Further, although the case where the coating film 14 is provided on thesurface of the sheath 13 of the cable 10 has been described, the presentinvention is not limited to this, but the coating film 14 can be appliedto a medical hollow tube such as a catheter or the like. Hereinafter, aspecific description will be given with reference to the drawings.

FIG. 4A is a cross-sectional view showing a medical hollow tube 70provided with an outer coating film 72 on an outer surface 71 a of ahollow tube main body 71. FIG. 4B is a cross-sectional view showing themedical hollow tube 70 provided with an inner coating film 73 on aninner surface 71 b of the hollow tube main body 71. FIG. 4C is across-sectional view showing the medical hollow tube 70 provided withthe outer coating film 72 and the inner coating film 73 on the outersurface 71 a and the inner surface 71 b, respectively, of the hollowtube main body 71.

The medical hollow tube 70 is configured to include a hollow tube mainbody 71, and an outer coating film 72 and/or an inner coating film 73that is covering a circumference (an outer surface 71 a or an innersurface 71 b or both the outer surface 71 a and the inner surface 71 b)of the hollow tube main body 71, the coating film adhering to the hollowtube main body 71. The hollow tube main body 71 may be formed of, forexample, a silicone rubber. The outer coating film 72 and/or the innercoating film 73 may be configured with the coating film 14 describedabove.

In this medical hollow tube 70, since the outer surface 71 a and theinner surface 71 b of the hollow tube main body 71 are excellent in theslidability, when the medical hollow tube 70 is brought into contactwith another member, the occurrence of the medical hollow tube 70 beingstuck can be suppressed, or when a device is inserted into the hollowtube 70, the device can be smoothly inserted therein or removedtherefrom.

Further, it is possible to suppress the formation of voids, which arederived from the air bubbles, in the surface of the outer coating film72 and/or the inner coating film 73 being contiguous to the hollow tubemain body 71. As a result, the area where the outer coating film 72and/or the inner coating film 73 is in contact with the hollow tube mainbody 71 can be maintained without being reduced, and the high adhesionstrength between the outer coating film 72 and/or the inner coating film73 and the hollow tube main body 71 can be ensured. More specifically,it is possible to allow the adhesion strength to be not lower than 0.30MPa.

EXAMPLES

Next, the present invention will be described in more detail based onexamples, but the present invention is not limited to these examples.

Example 1

(Production of Cable)

First, laid 200 coaxial cables each having a diameter of about 0.25 mmwere coated with a braided wire to produce a cable core (the cable core11). Subsequently, a sheath material was extruded at a rate of 5 m/minusing an extruder to coat an outer periphery of the cable core, on whichwas formed a sheath having a thickness of 0.8 mm (cable outer diameter:about 8 mm). A silicone rubber (“KE-541-U” available from Shin-EtsuChemical Co., Ltd.) was used as the sheath material.

Subsequently, materials to form a coating film (the coating film 14)were compounded. In Example 1, as a rubber component to compose thecoating film, an addition reaction type silicone rubber coating agent(trade name: SILMARK™, available from Shin-Etsu Chemical Co., Ltd.) wasprepared, and as fine particles to compose the coating film, siliconeresin fine particles having an average particle diameter of 5 μm (tradename: X-52-1621, available from Shin-Etsu Chemical Co., Ltd.) wereprepared. 120 parts by mass of the fine particles, 600 parts by mass oftoluene, which acts as a viscosity adjusting solvent, 8 parts by mass ofa crosslinking agent (trade name: CAT™, available from Shin-EtsuChemical Co., Ltd.), and 0.3 parts by mass of a curing catalyst (tradename: CAT-PL-2, available from Shin-Etsu Chemical Co., Ltd.) per 100parts by mass of the above rubber component were mixed together tocompound a coating solution having a proportion of the silicone resinfine particles to the coating film of 55% by mass. Further, 0.1% by massof hydrophobic fumed silica (trade name: AEROSIL®R972, available fromNippon Aerosil Co., Ltd.) was added to the above coating solution. Notethat the silicone resin fine particles content of the above-describedcoating film was calculated on the assumption that the coating agent wascured with substantially no decrease in mass (with the compounding massratio remaining substantially unchanged). Note that the composition ofthe above coating solution is shown in Table 1 below.

Subsequently, the surface of the sheath provided on the cable core wascleaned. Thereafter, the cable core provided with the sheath wasimmersed in the above-described coating solution by the dip coatingmethod to form a coating material layer made of the silicone rubber onthe surface of the sheath. In the present embodiment, the pulling upspeed for the cable core was set at 2 m/min. Thereafter, the coatingmaterial layer was subjected to a drying and curing treatment at atemperature of 150 degrees C. by heating with a heater (infrared heater)for 10 minutes to form the coating film having irregularities on itssurface. The thickness of the resulting coating film was 15 μm.

The above process produced a cable of Example 1.

TABLE 1 Example Example Example Example Comparative Comparative 1 2 3 4example 1 example 2 Coating film Rubber Rubber Addition 100 100 100 100— 100 composition component reaction type silicone rubber Condensation —— — — 100 — reaction type silicone rubber Fine particles Silicone resin120 150 120 120 13 120 fine particles Solvent Toluene 600 600 600 600 —600 Crosslinking agent 8 8 8 8 — 8 Curing catalyst 0.3 0.3 0.3 0.3 — 0.3Fumed silica (silica 0.1 0.1 — — — — fine particles) Coating filmthickness (μm) 15 17 15 15 15 15 Fine particles to coating filmproportion 55 60 55 55 56.5 55 (mass %) Pull-up speed of cable 2 m/min 2m/min 2 m/min 2 m/min 2 m/min 12 m/min Sheath Infrared absorber — — — 1— — Evaluation Coating film surface static friction 0.16 0.14 0.16 0.160.16 0.17 coefficient (μ) Adhesion strength between sheath and 0.40 0.320.39 0.44 0.22 0.40 coating film (MPa) Bending resistance ○ ○ ○ ○ × ○Wiping off Pre-testing static 0.16 0.14 0.16 0.16 0.16 0.17 resistancefriction coefficient (μ) Post-testing static 0.17 0.15 0.19 0.18 0.450.30 friction coefficient (μ) Difference 0.01 0.01 0.03 0.02 0.29 0.13between pre- and post-testing (μ) Surface No. of fine particles 94-9698-101 74-79 77-81 42-52 38-58 irregularities (/1600 μm²) No. of notsmaller None None None None 40 None than 1 μm voids (/1600 μm²) No.distribution of 1.05 1.51 3.27 2.53 10.6 19.6 fine particles (%) (Partsby mass with no unit of quantity required)

Example 2

In Example 2, a coating solution was compounded and a cable was producedin the same manner as in Example 1 except that the silicone rubber resinparticles content was changed from 120 parts by mass to 150 parts bymass, and the proportion of the silicone resin fine particles to thecoating film was changed to 60.0% by mass.

Example 3

In Example 3, a coating solution was compounded and a cable was producedin the same manner as in Example 1 except that the fumed silica was notadded.

Example 4

In Example 4, a coating solution was compounded and a cable was producedin the same manner as in Example 1 except that TiO₂ (the infraredabsorber) was added to the sheath material in such a manner that 1 partby mass of the infrared absorber is added per 100 parts by mass of thesheath material.

Comparative Example 1

In Comparative Example 1, a cable was produced using a condensationreaction type silicone rubber coating agent and silicone resin fineparticles having an average particle diameter of 5 μm (trade name:X-52-1621, available from Shin-Etsu Chemical Co., Ltd.). Note that, asthe coating agent, the condensation reaction type silicone rubbercoating agent including a vinyl oxime silane and a solvent (toluene,n-heptane) (trade name: X-93-1755-1, available from Shin-Etsu ChemicalCo., Ltd.) was used.

Comparative Example 2

In Comparative Example 2, a coating solution was compounded and a cablewas produced in the same manner as in Example 1 except that the pullingup speed of the cable was increased to be 12 m/min.

(Evaluation)

With respect to each cable produced above, the static frictioncoefficients of the respective coating film and the respective sheath,the adhesion strength between the respective coating film and therespective sheath, the bending resistance when the protective member wasattached, the resistance of the respective coating film to being wipedoff, and the surface irregularities of the respective coating film wereevaluated. Hereinafter, each measurement method will be described.

(Static Friction Coefficient)

First, a cut was made in the length direction in the respective sheathportion with the respective coating film thereon of each cable producedabove, and the respective underlying members included in each cableother than the respective sheath with the respective coating filmthereon were removed, and the respective sheath with the respectivecoating film thereon was spread out to produce a respective flat sheetthereof having a length of about 10 cm and a width of about 2.5 cm, anda respective 1.5 cm×1.5 cm square flat sheet thereof. A respective testsheet 1 with the respective flat sheet of the respective sheath with therespective coating film thereon having a length of about 10 cm and awidth of about 2.5 cm produced in the above manner and attached to aflat plate, and a respective sheet 2 with the respective 1.5 cm×1.5 cmsquare flat sheet of the respective sheath with the respective coatingfilm thereon produced in the above manner and attached to a flat platewere produced. The coated surface of the respective sheet 2 was opposedto and brought from above into contact with the coated surface or wipedoff coated surface of the respective test sheet 1, and with the flatplate of the respective sheet 2 being acted on by a load W of 2 N fromabove, the flat plate of the respective sheet 2 was pulled horizontallywith a push pull gauge, and the pulling force (frictional force) F forthe flat plate of the respective sheet 2 was measured. The staticfriction coefficient, μ, was calculated from F=μW. In the presentexamples, the static friction coefficient was calculated for each of therespective rubber compositions forming the respective coating films andthe respective rubber compositions forming the respective sheaths. Notethat, herein, the respective sheets 1 and 2 were prepared using thecables after the wiping off testing, and their coefficients of thestatic friction after the wiping off were measured.

(Adhesion Strength)

The adhesion strength between the underlying sheath and the overlyingcoating film was measured based on FIGS. 5 and 6 . FIG. 5 is a diagramfor explaining a method of producing an evaluation sample used forevaluating the adhesion strength between the underlying sheath and theoverlying coating film. FIG. 6 is a diagram schematically showing ameasuring method for measuring the tensile shear strength using theevaluation sample.

Specifically, first, a respective sample cable having a length of 100 mmwas sampled from each cable produced above. Further, a boot materialtube 52 (of inner diameter: about 8 mm, thickness: 0.8 mm, length: 100mm) was prepared, and a cut (a slit) 52 a was made in a length directionof that boot material tube. As shown in FIG. 5 , an adhesive 51 wasapplied to an outer peripheral surface of one end of the respectivesample cable 50. Subsequently, a portion of the one end of therespective sample cable 50 was wrapped with the boot material tube 52 insuch a manner that one section of the cut 52 a of the boot material tube52 is joined to another section, to bond the sample cable 50 and theboot material tube 52 together. Next, the respective underlying members(such as the respective cable core and the like) included in therespective sample cable 50 other than the respective sheath with therespective coating film thereon were pulled and removed to produce arespective sheath material tube 53 with the boot material tube 52 bondedand made integral therewith. Subsequently, a cut was made in the lengthdirection of the respective sheath material tube 53 with the bootmaterial tube 52 bonded and made integral therewith. At this point oftime, the cut was made in the respective sheath material tube 53 to becontinuous with the cut 52 a provided in the boot material tube 52. Thisresulted in a respective adhesion strength evaluating sample 54 as shownin FIG. 6 . Note that the respective sheath material tube 53 and theboot material tube 52 were formed using the same silicone rubbers(static friction coefficient: not lower than 1.0). As the adhesive 51, acommercially available silicone based adhesive KE-45 (available fromShin-Etsu Chemical Co., Ltd.) was used. The bonding region at this pointof time was, for example, 10 mm in length×25 mm in outer circumference,and the thickness of the adhesive 51 was on the order of 50 μm to 200μm. The respective evaluation sample 54 produced in this manner was leftto stand in the atmosphere at 25 degrees C. for 168 hours.

The adhesion strength between the respective sheath material tube 53 andthe respective coating film was evaluated by measuring the tensile shearstrength using the respective evaluation sample 54. Specifically, asshown in FIG. 6 , opposite end portions of the sheath material tube 53and the boot material tube 52 made integral with each other were grippedand pulled at a speed of 500 mm/min, and the tensile shear strength wasmeasured, and the adhesion strength between the sheath material tube 53and the coating film was measured. Note that the gripping positions forthe opposite end portions of the sheath material tube 53 and the bootmaterial tube 52 made integral with each other were adjusted in such amanner that the distance between the gripped opposite end portions ofthe sheath material tube 53 and the boot material tube 52 made integralwith each other was 70 mm. In the present examples, when the adhesionstrength was not lower than 0.30 MPa, the adhesion strength wasevaluated as the enough adhesion strength.

(Bending Resistance)

The bending resistance was evaluated by bonding a boot to one end ofeach cable 10 produced above as a protective member with a siliconebased adhesive KE-45 to produce a probe cable, repeatedly bending thatprobe cable and measuring the adhesion strength of that boot to thecable. The sheath and the boot were made of the same silicone rubber(“KE-541-U” available from Shin-Etsu Chemical Co., Ltd.). A bonding areabetween the probe cable and the boot was 250 mm² (the size of thebonding region is a longitudinal length of 10 mm and an outercircumferential length of 25 mm).

Specifically, the evaluation of the bending resistance was made as shownin FIG. 7 . FIG. 7 is a diagram schematically illustrating a bendingresistance testing for the probe cable (a length of 1 m). First, a loadof 500 g was applied to the probe cable 60, and a part of the boot 61attached to the end portion of the probe cable 60 was held in such amanner that the probe cable 60 was held in the vertical position, andthe operation of bending the held part of the boot 61 to the right by 90degrees and to the left by 90 degrees alternately at a rate of 30times/minute was repeatedly performed. Herein, a series of operations offirst holding the held part of the boot 61 in the vertical position,then bending it to the left by 90 degrees, again returning it to thevertical position, then bending it to the right by 90 degrees, and againreturning it to the vertical position was counted as one time bendingoperation. The operation of bending the held part of the boot 61 to theright and to the left alternately was repeatedly performed 150,000 timesor more in total. In the present examples, when no peeling or fractureof the boot 61 occurred in the above bending resistance testing, thebending resistance was determined as good (o), or when a peeling orfracture of the boot 61 occurred in the above bending resistancetesting, the bending resistance was determined as poor (x).

(Wiping Off Resistance)

The resistance of the coating film 14 to being wiped off was evaluatedby a testing shown in FIGS. 8A and 8B repeatedly wiping off the surfaceof the coating film 14 with a cotton cloth impregnated with adisinfecting alcohol. FIG. 8A is a diagram for explaining the wiping offtesting method. FIG. 8B is a diagram for explaining a wiping directionlength of the cotton cloth and a wiping off length by moving the cottoncloth. Specifically, first, as shown in FIG. 8A, a string 81 was tied toone end of the cable 10 (length 10 m), and the string 81 was passedaround a pulley 82 and a guide pulley 83, and was joined to a rotatablerotating circular plate 84. The cable 10 was hung and a weight 85 of 400g was tied to a lower end portion of the cable 10. This allowed thecable 10 to be held to be able to be reciprocated upward and downward inthe vertical direction by the rotation of the rotating circular plate84. Then, a cotton-like gauze cloth (length 50 mm along the wipingdirection of the cotton cloth) was wrapped around the surface of thecoating film 14 of the cable 10 as a cotton cloth 86. The cotton cloth86 was pre-impregnated with a disinfecting ethanol (including 75% to 80%ethanol). Subsequently, the wrapped cotton cloth 86 was held to becovered with wiper holders 87 and 87 made of a silicone rubber sponge(hereinafter also referred to as “holders 87”), and the holders 87 wereadjusted in such a manner that the cotton cloth 86 is brought contiguousto the surface of the coating film 14 at a shearing stress of 2×10⁻³ MPato 4×10⁻³ MPa. Subsequently, by reciprocating the cable 10 upward anddownward relative to the holders 87, the surface of the coating film 14of the cable 10 was wiped off with the cotton cloth 86 held in theholders 87. In the present examples, as shown in FIG. 8B, the wipingdirection length X of the cotton cloth 86 was set at 50 mm, the wipingoff length Y (moving distance Y) of the cable 10 by the cotton cloth 86was set at 150 mm, and a one-way moving distance of the cotton cloth 86was set at 200 mm. Further, the cable 10 was reciprocated 40 to 60 timesper minute, and the wiping off speed for the surface of the coating film14 was set at a speed of 80 times/min to 120 times/min (40 cycles/min to60 cycles/min). Also, every time the cable 10 was reciprocated 500 timesrelative to the cotton cloth 86, the cotton cloth 86 was replaced with anew one. In the present examples, the static friction coefficient on thesurface of the coating film 14 after 20,000 wiping off operations(10,000 reciprocations) was measured, and the difference (the absolutevalue of the difference) between the static friction coefficients of thecoating film 14 before and after the testing, (<static frictioncoefficient after the testing>−<static friction coefficient before thetesting>), was calculated. When the difference (the absolute value ofthe difference) between the static friction coefficients of the coatingfilm 14 before and after the testing was not greater than 0.1, the cable10 was evaluated as having less damage to the coating film 14 due to thewiping off, and was evaluated as excellent in the resistance of thecoating film 14 to being wiped off. Note that the environmentaltemperature was set at 25±3 degrees C., and the environmental humiditywas 50±10%.

As the cotton cloth 86, “BEMCOT regular type (M-3II), size 250 mm×250mm, quarter-fold type” available from Asahi Kasei Corporation, which isa long fiber non-woven fabric including cotton linters, was used. Asingle BEMCOT (folded in four) was unfolded and a piece with a size of50 mm×175 mm was cut out from the cloth with a size of 250 mm×250 mm.The cut piece of BEMCOT was entirely and uniformly impregnated with thedisinfecting alcohol (approximately 2.5 ml) dropped from a dropper.Next, the cut piece of BEMCOT impregnated with the disinfecting alcoholwas wrapped around the cable 10 (by approximately 7 cycles) in such amanner that a long side of the cut piece of BEMCOT coincides with acircumferential direction of the cable 10. Here, the long side length ofthe cut piece of BEMCOT was adjusted based on an outer diameter of thecable 10 in order to wind the cut piece of BEMCOT around the cable 10 byapproximately 7 cycles.

Further, in the wiping off testing, after the cotton cloth 86 has beenreciprocated 250 times, 2.5 ml of the disinfecting alcohol was suppliedas liquid droplet to the cotton cloth 86, for maintaining theimpregnation status of the cotton cloth 86 with the alcohol. This liquiddroplet was made by dropping the disinfecting alcohol by the dropper onan upper end of the cotton cloth 86 held by the holders 87 along thecircumferential direction of the cable 10 such that the cotton cloth 86is impregnated with the disinfecting alcohol. Note that the additiveamount of the disinfecting alcohol may be determined in order not to drythe cotton cloth due to volatilization at the time of reciprocating thecotton cloth 86 for 250 times in the wiping off testing. In the presentExamples, the additive amount was adjusted to be 2.5 ml.

Further, a force to bring the cotton cloth 86 contiguous to the cable 10(the shearing stress) was adjusted as follows. The cotton cloth 86prepared by the above method was wrapped around the cable 10 and held tobe covered with wiper holders 87 and 87. Next, one end of the cable 10held by the holders 87 was pulled horizontally by a push pull gauge(push pull scale), and the shearing stress obtained by dividing a forcewhen the cable 10 started to move with respect to the holders 87 by asurface area of the cable 10 covered by the wiper holders 87, 87 wasadjusted to be within a range of 2×10⁻³ MPa to 4×10⁻³ MPa. Each of theholders 87 was made of the silicone rubber sponge and provided with arecess at a portion contacting the cable 10 wrapped with the cottoncloth 86. The recesses of the holders 87, 87 were processed to have acylindrical shape when the holders 87, 87 are combined with each other.In the case where the shearing stress was out the predetermined range,the holding force (clamping force) of the wiper holders 87, 87 wasadjusted by changing the size (diameter) of the recesses of the wiperholders 87, 87 (parts for holding the cable 10). Note that the shearingstress was adjusted each time when the cotton cloth 86 was changed.

The weight 85 is a driving source for moving the cable 10 downwardly(free fall) and may be weighted in such a manner that a time requiredfor moving the cotton cloth 86 downwardly for 200 mm would be 0.67sec/cycle to 1 sec/cycle (40 cycles/min to 60 cycles/min). Here, at thetime of adjusting the shearing stress, the weight 85 was set in such amanner that the gravity to the weight 85 would be 1.5 times to 2 timesof the force when the cable 10 starts to move with respect to the wiperholders 87, 87 (the product of the shearing stress by the surface areaof the cable 10 covered by the wiper holders 87, 87).

(Surface Irregularities)

The surface irregularities of the coating films were evaluated byobserving the surfaces of the coating films with an electron microscope,and counting the number of fine particles and the number of voidspresent per unit area, and calculating the number distribution of thefine particles.

The number of the fine particles and the number of the voids per unitarea were calculated by observing the surfaces of the coating films withthe electron microscope.

For the number distribution of the fine particles, first, an image ofthe surface of each of the coating films was photographically recordedat a magnification of 1000 times, and four regions of 40 μm×40 μm on thesurface of each of the coating films were optionally selected, thenumbers of the fine particles present in each of the four regions werecounted, and the number of the fine particles per unit area wascalculated. And when, of the numbers of the fine particles present ineach of the four regions, the maximum value was denoted by N_(max) andthe minimum value was denoted by N_(min), the number distribution, whichwas calculated from the formula ((N_(max)−N_(min))/+N_(min)))×100, wascalculated. In the present examples, when the calculated numerical valuefor the number distribution of the fine particles was not more than 5%,the variation in the number of the fine particles was evaluated assmall.

(Evaluation Results)

Table 1 summarizes the evaluation results. As shown in Table 1, inExamples 1 to 4, the static friction coefficients of their respectivecoating films were 0.5 or less, and it was confirmed that theirrespective coating films were excellent in the slidability. Further, inExamples 1 to 4, since the strengths of the adhesion between theirrespective coating films and their respective sheaths were not lowerthan 0.3 MPa, and no peeling of the boot occurred even in the bendingtesting, it was confirmed that the strengths of the adhesion of theirrespective coating films were high.

Also, in Examples 1 to 4, regarding the resistance of their respectivecoating films to being wiped off, even after their respective coatingfilms were repeatedly wiped off, the static friction coefficients oftheir respective coating films were not varied significantly as comparedto those calculated before the testing, so it was confirmed that thedifferences between the static friction coefficients of their respectivecoating films before and after the testing were not greater than 0.1.

Here, the change in the static friction coefficient of the coating filmof Example 1 due to the wiping off operations will be specificallydescribed with reference to FIG. 9 . FIG. 9 is a diagram showing thechanges in the static friction coefficients of the coating filmsaccording to the number of times of wiping off, where the horizontalaxis represents the number of times of wiping off [times], and thevertical axis represents the static friction coefficient of the coatingfilms. In FIG. 9 , regarding the changes in the static frictioncoefficients of the coating films, Example 1 was indicated by circular(∘) plotting, Example 1 (∘), Example 2 was indicated by a square (□)plotting, and Example 3 was indicated by a triangle (Δ) plotting, whileComparative Example 1 was indicated by a diamond (⋄) plotting, andComparative Example 2 was indicated by a cross (x) plotting, and as areference example, the static friction coefficients of a coating filmmade of a polyvinyl chloride (PVC) was indicated by asterisk (*)plotting. As shown in FIG. 9 , the static friction coefficient of thecoating film of Example 1 was 0.16 before the wiping off testing, andwas 0.17 after the coating film of Example 1 was wiped off 20,000 times,thus it was confirmed that the difference (the absolute value of thedifference) between the static friction coefficients of the coating filmof Example 1 before and after the testing was 0.01. Further, the staticfriction coefficient of the coating film of Example 2 was 0.14 beforethe wiping off testing, and was 0.15 after the coating film of Example 2was wiped off 20,000 times, and thus it was confirmed that thedifference (the absolute value of the difference) between the staticfriction coefficients of the coating film of Example 2 before and afterthe testing was 0.01. The static friction coefficient of the coatingfilm of Example 3 was 0.16 before the wiping off testing, and was 0.19after the coating film of Example 3 was wiped off 20,000 times, thus itwas confirmed that the difference (the absolute value of the difference)between the static friction coefficients of the coating film of Example3 before and after the testing was 0.03. The static friction coefficientof the coating film of Example 4 was 0.16 before the wiping off testing,and was 0.18 after the coating film of Example 4 was wiped off 20,000times, thus it was confirmed that the difference (the absolute value ofthe difference) between the static friction coefficients of the coatingfilm of Example 4 before and after the testing was 0.02. That is, it wasconfirmed that, in Examples 1 to 4, even after their respective coatingfilms were wiped off 20,000 times, the static friction coefficients oftheir respective coating films were not greatly varied, so theirrespective coating films were able to be kept high in the slidability,and were excellent in the resistance to being wiped off. In addition, itwas confirmed that the static friction coefficients of the respectivecoating films of Examples 1 to 4 were able to be kept lower than that ofthe PVC coating film.

On the other hand, in Comparative Example 1, it was confirmed that,although the coating film was excellent in the slidability, not only theadhesion strength between the sheath and the coating film was low butalso the resistance of the coating film to being wiped off was low.Specifically, in Comparative Example 1, the adhesion strength betweenthe sheath and the coating film was 0.22 MPa, and the boot was peeledoff by the bending testing. As indicated by the diamond (⋄) plotting inFIG. 9 , the static friction coefficient of the coating film ofComparative Example 1 was 0.16 before the wiping off testing, and was0.45 after the coating film of Comparative Example 1 was wiped off20,000 times, thus the difference (the absolute value of the difference)between the static friction coefficients of the coating film ofComparative Example 1 before and after the testing was 0.29. InComparative Example 1, the static friction coefficient of the coatingfilm was gradually increased by repeating the wiping off, and theslidability of the coating film was not able to be maintained. That is,it was confirmed that the coating film of Comparative Example 1 was poorin the resistance to being wiped off.

In Comparative Example 2, it was confirmed that, although the coatingfilm was excellent in the slidability and the adhesion strength betweenthe sheath and the coating film but also the resistance of the coatingfilm to being wiped off was lower than Examples 1 to 3. As indicated bythe cross (x) plotting in FIG. 9 , the static friction coefficient ofthe coating film of Comparative Example 2 was 0.17 before the wiping offtesting, and was 0.30 after the coating film of Comparative Example 2was wiped off 20,000 times, thus the difference (the absolute value ofthe difference) between the static friction coefficients of the coatingfilm of Comparative Example 2 before and after the testing was 0.13. InComparative Example 2, the static friction coefficient of the coatingfilm was gradually increased by repeating the wiping off, and theslidability of the coating film was not able to be maintained. That is,it was confirmed that the coating film of Comparative Example 2 was poorin the resistance to being wiped off in comparison with Examples 1 to 3.

This difference in the properties is due to the distribution of the fineparticles on the surface of the coating film and the resulting surfaceirregularities shape. Hereinafter, these points will be described.

For each of the Examples 1 to 4 and Comparative Examples 1 and 2, thesurface irregularities and cross section of the coating film before thewiping off testing were checked, and as a result, it was observed thatthe surfaces of the coating films of the Examples 1 to 4 and ComparativeExamples 1 and 2 were in states as shown in FIGS. 10A, 10B, 11A, 11B, 12and 13 respectively. FIG. 10A is an SEM image showing the surface of thecoating film of Example 1. FIG. 10B is an SEM image showing the crosssection of the coating film of Example 1. FIG. 11A is an SEM imageshowing the surface of the coating film of Comparative Example 1. FIG.11B is an SEM image showing the cross section of the coating film ofComparative Example 1. FIG. 12 is an SEM image showing a cross sectionof the coating film of the cable of Example 3. FIG. 13 is an SEM imageshowing a coating film surface of a cable of Comparative Example 2.Comparing these figures, it was observed that, in the coating film ofExample 1, the fine particles were densely distributed, whereas, inComparative Example 1 and Comparative Example 2, not only the fineparticles but also the collapse formations (the portions shown in blackin FIGS. 11A and 11B) were present. In addition, it was observed that,in the coating film of Comparative Example 1, the air bubbles (voids)were present over a wide range on the surface of the coating film beingcontiguous to the sheath, whereas, in the coating film of Example 1, theair bubbles (voids) were reduced as compared with Comparative Example 1.In Comparative Example 2, the air bubbles were not observed but thenumber of the fine particles existing at the surface were low and thedistribution thereof was sparse.

As a result of counting the number of the fine particles based on theSEM image, the number of the fine particles in Example 1 was 94 to 96per 1600 μm² area (40 μm square), the number of the fine particles inExample 2 was 98 to 101 per 1600 μm² area (40 μm square), the number ofthe fine particles in Example 3 was 74 to 79 per 1600 μm² area (40 μmsquare), and the number of the fine particles in Example 4 was 77 to 81per 1600 μm² area (40 μm square), whereas the number of the fineparticles in Comparative Example 1 was 42 to 52 per 1600 μm² area (40 μmsquare), and the number of the fine particles in Comparative Example 2was 38 to 58 per 1600 μm² area (40 μm square). That is, Examples 1 to 4were larger in the number of the distributed fine particles thanComparative Examples 1 and 2. Further, in Examples 1 to 4, substantiallyno void having a size of not smaller than 1 μm was present, whereas inComparative Example 1, at least 40 voids having a size of not smallerthan 1 μm were present within the range of 40 μm square. Further, as aresult of calculating the number distribution of the fine particles fromthe number of the fine particles in each region, the number distributionof the fine particles was 1.05% in Example 1, 1.51% in Example 2, 3.27%in Example 3, and 2.53% in Example 4, so the variation in the numberdistribution of the fine particles was small, namely, not larger than 5%in all the Example 1 to 4. On the other hand, the number distribution ofthe fine particles was 10.6% in Comparative Example 1, and 19.6% inComparative Example 2, so the distribution of the fine particles in thecoating film was not uniform, and the variation in the numberdistribution of the fine particles was large.

Furthermore, as a result of obtaining the surface profiles for therespective coating films of Example 1 and Comparative Example 1, resultsas shown in FIGS. 14 and 15 were obtained. FIG. 14 is a diagram showingthe surface profile for the coating film of Example 1. FIG. 15 is adiagram showing the surface profile for the coating film of ComparativeExample 1. As shown in FIG. 14 , in the coating film of Example 1, nocollapse formation due to void formation was observed, so it wasconfirmed that the projecting portions formed by the fine particles werepresent in larger quantity than the quantity of the collapsed portiondue to the collapse formation. On the other hand, in Comparative Example1, as shown in FIG. 15 , it was confirmed that the collapsed portionsdue to the collapse formations were present in large quantity on thesurface of the coating film.

The collapses formed in the coating film were caused by the air bubblesformed as a result of a condensation reaction when the condensationreaction type silicone rubber was cured. When the coating film was wipedoff with the cotton cloth, the above collapses formed in the coatingfilm caused the cotton cloth to be easily stuck at the edges of thecollapses, and therefore the coating film was easily damaged by beingwiped off with the cotton cloth. As a result, in Comparative Example 1,the fine particles in the coating film were considered to fall off bythe coating film being wiped off, thereby tending to increase the staticfriction coefficient of the coating film, and failing to maintain theslidability of the coating film over a long period of time. Further, thepresence of the voids in the contact surface of the coating film withthe underlying sheath was also considered to reduce the contact areabetween the coating film and the underlying sheath, and thereby lowerthe adhesion strength therebetween.

In this regard, in the present examples, the use of the additionreaction type silicone rubber allowed suppressing the formation of theair bubbles resulting from the curing of the addition reaction typesilicone rubber, and thereby reducing the collapse formation on thesurface of the coating film and the void formation in the coating film.In addition, preferably, the self-ordering of the fine particles waspromoted by adjusting the pulling up speed for the cable when applyingthe coating material by the dipping method. According to Example 1 andComparative Example 2, it was found that the distribution variation ofthe fine particles in the coating film largely changes depending on thepulling up speed for the cable. In Comparative Example 2, the pulling upspeed for the cable was excessively increased so that the self-orderingof the fine particles was not promoted and the number of the fineparticles was 38 to 58 per unit area, namely, the distribution of thefine particles was sparse in comparison with Example 1 (94 to 96 perunit area). Further, it was confirmed that the number distribution ofthe fine particles was 19.6%, so that the distribution variation islarger than 1.05% in Example 1. As a result, it is assumed that thestatic friction coefficient of the coating film tends to be increaseddue to the falling out of the fine particles or the like by the wipingoff so that the slidability was not maintained in Comparative Example 2.

Further, according to Examples 1 and 3, the fine particles can bedistributed more densely at the surface of the coating film by addingthe fumed silica to the rubber composition. As a result, it is possibleto achieve the coating film which is more excellent in the slidability,the adhesion strength between the coating film and the sheath, and theresistance to being wiped off.

As a result of comparison between Example 3 and Example 4, it wasconfirmed that the adhesion strength between the coating film and thesheath can be increased by compounding the infrared absorber as inExample 4 more than Example 3 in which the infrared absorber was notcompounded.

Preferred Aspects of the Present Invention

Hereinafter, preferred aspects of the present invention will bedescribed.

Supplementary Description 1

According to one embodiment of the present invention, aspect of thepresent invention, there is provided a cable, comprising: a sheath; anda coating film covering a circumference of the sheath, the coating filmadhering to the sheath, wherein the coating film comprises a rubbercomposition including a rubber component and fine particles, with astatic friction coefficient on a surface of the coating film being 0.5or less, wherein the coating film comprises a resistance to being wipedoff in such a manner that, when the coating film is subjected to atesting such that a long fiber non-woven fabric including cotton lintersincluding an alcohol for disinfection with a length of 50 mm along awiping direction is brought contiguous to the surface of the coatingfilm at a shearing stress of 2×10⁻³ MPa to 4×10⁻³ MPa, followed bywiping off the surface of the coating film at a speed of 80 times/min to120 times/min and 20,000 repetitions thereof for a wiping directionlength of 150 mm, a difference (an absolute value of a difference)between the static friction coefficients of the coating film before andafter the testing is not greater than 0.1.

Supplementary Description 2

In the aspect of supplementary description 1 above, an adhesion strengthbetween the sheath and the coating film is 0.30 MPa or more.

Supplementary Description 3

In the aspect of supplementary description 1 or 2 above, the rubbercomponent is at least one of a silicone rubber and a chloroprene rubber.

Supplementary Description 4

In the aspects of supplementary descriptions 1 to 3 above, the rubbercomponent is a silicone rubber, while the fine particles include atleast any one of silicone resin fine particles, silicone rubber fineparticles, and silica fine particles.

Supplementary Description 5

In the aspects of supplementary descriptions 1 to 4 above, the fineparticles have a higher hardness than that of the rubber component.

Supplementary Description 6

In the aspects of supplementary descriptions 1 to 5 above, the fineparticles comprise an average particle diameter of 1 μm or more and 10μm or less.

Supplementary Description 7

In the aspects of supplementary descriptions 1 to 6 above, the coatingfilm comprises a thickness of 3 μm or more and 100 μm or less.

Supplementary Description 8

In the aspects of supplementary descriptions 1 to 7 above, the sheathcomprises a silicone rubber.

Supplementary Description 9

In the aspects of supplementary descriptions 1 to 6 above, the rubbercomponent is an addition reaction type silicone rubber.

Supplementary Description 10

In the aspects of supplementary descriptions 1 to 9 above, when thenumber of the fine particles per unit area is measured in any pluralityof parts of the surface of the coating film, a number distribution,which is calculated from a formula(N_(max)−N_(min))/(N_(max)+N_(min))×100 where N_(max) is a maximum valueof the number of the fine particles per unit area and N_(min) is aminimum value of the number of the fine particles per unit area, is notmore than 5%.

Supplementary Description 11

In the aspects of supplementary descriptions 1 to 10 above, in thesurface of the coating film, the number of voids comprising a size ofnot smaller than 1 μm present per unit area is not more than 5/40 μmsquare.

Supplementary Description 12

In the aspects of supplementary descriptions 1 to 11 above, a quantityof the fine particles in the rubber composition is not lower than 10% bymass and not higher than 60% by mass to a total of the rubber componentand the fine particles.

Supplementary Description 13

In the aspects of supplementary descriptions 1 to 12 above, the cable isconfigured to be connectable to a medical device.

Supplementary Description 14

In the aspects of supplementary descriptions 1 to 13 above, the sheathfurther comprises an infrared absorber.

Supplementary Description 15

In the aspects of supplementary description 14 above, a content of theinfrared absorber is 0.1% by mass to 10% by mass per 100 parts by massof a material of the sheath.

Supplementary Description 16

In the aspects of supplementary description 14 or 15 above, the infraredabsorber comprises titanium oxide.

Supplementary Description 17

According to another aspect of the present invention, there is provideda medical hollow tube, comprising: a hollow tube main body including aninner surface and an outer surface; and a coating film covering at leastone of the inner surface and the outer surface of the hollow tube mainbody, the coating film adhering to the hollow tube main body, whereinthe coating film comprises a rubber composition including a rubbercomponent and fine particles, with a static friction coefficient on asurface of the coating film being 0.5 or less, wherein the coating filmcomprises a resistance to being wiped off in such a manner that, whenthe coating film is subjected to a testing such that a long fibernon-woven fabric including cotton linters including an alcohol fordisinfection with a length of 50 mm along a wiping direction is broughtcontiguous to the surface of the coating film at a shearing stress of2×10⁻³ MPa to 4×10⁻³ MPa, followed by wiping off the surface of thecoating film at a speed of 80 times/min to 120 times/min and 20,000repetitions thereof for a wiping direction length of 150 mm, adifference (an absolute value of a difference) between the staticfriction coefficients of the coating film before and after the testingis not greater than 0.1.

Supplementary Description 18

In the aspects of supplementary description 17 above, the hollow tubemain body further comprises an infrared absorber.

Supplementary Description 19

In the aspects of supplementary description 18 above, a content of theinfrared absorber is 0.1% by mass to 10% by mass per 100 parts by massof a material of the hollow tube main body.

Supplementary Description 20

In the aspects of supplementary description 18 or 19 above, the infraredabsorber comprises titanium oxide.

Although the invention has been described with respect to the specificembodiments for complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

What is claimed is:
 1. A medical hollow tube, comprising: a hollow tubemain body including an inner surface and an outer surface; and a coatingfilm covering at least the outer surface of the hollow tube main body,the coating film adhering to the hollow tube main body, wherein thecoating film comprises an addition reaction type silicone rubbercomposition and fine particles that form surface irregularities toreduce a static friction coefficient of the coating film, with a staticfriction coefficient on a surface of the coating film being betweenabout 0.1 and 0.5 as measured against itself when a normal force of 2 Nis applied in an environmental temperature of 25±3 degrees C., and anenvironmental humidity of 50±10%, wherein the coating film comprises aresistance to being wiped off in such a manner that, when the coatingfilm is subjected to a testing such that a long fiber non-woven fabricincluding cotton linters including an alcohol for disinfection with alength of 50 mm along a wiping direction is brought contiguous to thesurface of the coating film at a shearing stress of 2×10⁻³ MPa to 4×10⁻³MPa, followed by wiping off the surface of the coating film at a speedof 80 times/min to 120 times/min and 20,000 repetitions thereof for awiping direction length of 150 mm, the absolute value of a differencebetween the static friction coefficients of the coating film before andafter the testing is not greater than 0.1, wherein, in the surface ofthe coating film, the number of voids comprising a size equal to orlarger than 1 μm is not more than 5 per 40 μm×40 μm area, wherein, whenthe number of the fine particles visible at a magnification level of1000×in a 40 μm×40 μm area is measured in four different areas of thesurface of the coating film, a number distribution, which is calculatedfrom a formula (Nmax−Nmin)/(Nmax+Nmin)×100 where Nmax is a maximum valueof the number of the fine particles in the four 40 μm×40 μm areas andNmin is a minimum value of the number of the fine particles of the four40 μm×40 μm areas, is not more than 5%, and wherein the fine particleshave a higher hardness than that of the silicone rubber composition. 2.The medical hollow tube according to claim 1, wherein an adhesionstrength between the hollow tube main body and the coating film isbetween about 0.30 MPa and 0.70 MPa.
 3. The medical hollow tubeaccording to claim 1, wherein the fine particles include at least anyone of silicone resin fine particles, silicone rubber fine particles,and silica fine particles.
 4. The medical hollow tube according to claim1, wherein the fine particles comprise an average particle diameter of 1μm or more and 10 μm or less.
 5. The medical hollow tube according toclaim 1, wherein the coating film comprises a thickness of 3 μm or moreand 100 μm or less.
 6. A medical hollow tube, comprising: a sheath; anda coating film covering the outer circumference of the sheath, thecoating film adhering to the sheath, wherein the coating film comprisesa rubber composition including an addition reaction type silicone rubberand fine particles that form surface irregularities to reduce a staticfriction coefficient of the coating film, with a static frictioncoefficient on a surface of the coating film being between about 0.1 and0.5 as measured against itself when a normal force of 2 N is applied inan environmental temperature of 25±3 degrees C., and an environmentalhumidity of 50±10%, wherein the coating film comprises a resistance tobeing wiped off in such a manner that, when the coating film issubjected to a testing such that along fiber non-woven fabric includingcotton linters including an alcohol for disinfection with a length of 50mm along a wiping direction is brought contiguous to the surface of thecoating film at a shearing stress of 2×10⁻³ MPa to 4×10⁻³ MPa, followedby wiping off the surface of the coating film at a speed of 80 times/minto 120 times/min and 20,000 repetitions thereof for a wiping directionlength of 150 mm, the absolute value of a difference between the staticfriction coefficients of the coating film before and after the testingis not greater than 0.1, and wherein, in the surface of the coatingfilm, the number of voids comprising a size equal to or larger than 1 μmis not more than 5 per 40 μm×40 μm area, wherein when the number of thefine particles visible at a magnification level of 1000× in a 40 μm×40μm area is measured in four different areas of the surface of thecoating film, a number distribution, which is calculated from a formula(Nmax−Nmin)/(Nmax+Nmin)×100 where Nmax is a maximum value of the numberof the fine particles in the four 40 μm×40 μm areas and Nmin is aminimum value of the number of the fine particles of the four 40 μm×40μm areas, is not more than 5%, and wherein the fine particles have ahigher hardness than that of the silicone rubber composition.